BTW, there are other 'Highwayman' videos on Youtube which feature another, far more interesting truck:

This vehicle is clearly way in advance of what a low-budget TV series prop department could produce, so I did some Googling and find that it is based on a real vehicle called the 'Steinwinter', produced in Germany:

For some reason Google also threw-up this picture, which brings us back to the subject of buses (slightly):

I very seriously looked into buying a 53 foot trailer and semi tractor for conversion into an RV. The unit I was looking at had already been retitled as a motorhome. I traveled all the way from Minneapolis to Indiana to look at it. The biggest reason I didn't do it was I couldn't get insurance. There is no way I could ever get into an RV park, but I had no intention of ever going to an RV park anyhow.

The other issue was lack of space for travelers. I have had up to 9 people in my bus. A semi tractor would be lucky to seat more than 4 or 5 people if the bunk was removed.